Reduction of ores



28, 193). F DUFFlELD 1,779,411

REDUCTION OF ORES Filed Sept. 21, 1928 2 Sheets-Sheet l Jwm FZE DERJCK Z/NDLEYflUFF/ELD,

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F. L. DUFFIELD 1,779,411

REDUCTION OF OHES Filed Sept. 21, 1928 2 Sheets-Sheet 2 Imam" fkEDE/YMKKHVZMEY Hui-FIELD,

Patented Oct. 28, 1930 UNITED STATES PATENT OFFICE BEDUC'IION OF ORES Application filed September 21, 1928, Serial No This invention relates to the reduction of iron ores.

In standard practice the ore is charged at the top of the reducing chamber, and trav- U erses from top to bottom, the gases evolved flowing in the opposite direction, i. e., from bottom to top. The maximum temperature is at the bottom of the furnace and the coldest zone is at the top, and economy is sought in producing the maximum amountof CO present in the exit gases of the reducing furn'ace compatible with eflicient gaseous reduction, such as obtains in the blast furnace or electric smelting furnace.

The object of the present invention is to provide an improved process.

According to the present invention the ore charge and the gases evolved in the reducing chamber moves in the same direction.

Further, according to the present invention, the gases evolved in the reducing chamber pass through progressively hotter zones in the said reducingchamber.

A preferred way of carrying out the present 25 invention will be described by way of example with reference to the drawings filed herewith, wherein Fig. 1 is an end part sectional view the left half of which is takenon line A-B, Fig. 2,

' so and the right half of which is taken on line CD, Fig. 2;

Fig. 2 is a side view also partly in section; and

Figs. 3, 4 and 5 are detail views. The apparatus shown in the drawing shows a five battery retort and comprises a series of reducing chambers 10 disposed between combustion chambers 11. The partition walls between the chambers 10 and 11 are built of hollow refractory bricks. A hydraulic ram 12 working in a cylinder 13 is disposed at the base of each chamber 10, and is arranged in association with another hydraulic ram 14 working in a cylinder 15, hereinafter referred 4 to as the feed ram. The charge is fed as required through a chute 16 to the cylinder 15, and is fed to the cylinder 13 in the following way. The ram12 is shown in Fig. 1 at the top of its stroke, and as it travels downward and approaches the bottomof its stroke, the ram double walled, the inner wall being cooled by 307,413, and in Great Britain October 10, 1927.

14 is withdrawn and allows a further supply of ore to be fed into the cylinder 15, which is pushed by the subsequent forward movement of the ram 14 into the cylinder 13 on top'of the ram 12. A one-way cock 1, shown in de- 55 tail in Figs. 3, 4 and 5, is provided at the base of the chamber 10. This cock is operated by a ram rod 2 to close the base of the chamber during the downward movement of the ram 12, and to provide a passage between the cylinder 13 and the chamber 10, when the ram 12 is pushing upwards a further charge. The ram rods 12 13 and 2 are operably connected by suitable link mechanism so that the movements of the rams 12 and 14 and the oneway cock 1 are automatic and are sychronized relatively to one another. The rams may be operated electrically or mechanically.

The ore is reduced on its travel through the chamber 10, and the reduced material on approaching the top of the said chamber is conveyed by ducts 20 through water cooled passages 5 to spiral conveyors 21, and conveyed elsewhere for treatment. The ducts 20 are a current of air entering through the inlets 32 and travelling between the double walls. The heated air thus obtained passes at the top of the ducts 20 into a collecting pipe 6, and is fed into a common hot air main 7 mounted above the battery, for use as hereafter described.

Thegases evolved in the reducing chambers 10 pass out through a passage 22 provided at the top of each chamber 10 and are collected in a common pipe 23, which supplies the combustion chambers 11. the hot gases being admitted into the said chambers through inlets 8. Hot air is supplied to the chambers 11 from the main 7 through apertures 9, and the hot gases and hot air pass down the chambers 11. whilst burning. The waste gases are collected at the bottom of the combustion chambers through exit ports 30 communicating with a common main 31, and are passed to a waste heat recovery plant or otherwise disposed of. p The operation of reduction takes place as follows: The ore is ground and mixed with ground coal containing the requisite carbon for performing the reduction of the ore to the metal. The mixture is fed into the chutes 16,

and is delivered as required into the cylinders 15, and pushed by the feed rams 14: into the cylinders 13, on top of the rams 12, the rams 14 closing the sides of the cylinders 13, while the rams 12 are forcing the charge up. The rams 12 have a limited reciprocating moveinent, and on each upward stroke they force the charge up, so that each stroke causes a quantity of the reduced charge to fall through the ducts 20 and on to the conveyors 21. The reduced material may then be cooled and conveyed to a magnetic separator for extraction of the iron particles, which can be stamped into blocks for use as a substitute for pig iron or scrap iron.

"On the downward stroke of the ram 12 the charge is supported in the reducing chamber by means of the one-way cock 1 as above described. When starting the furnace after the chambers have been filled, an outside source of gas is employed, and is burnt at the top of the combustion chambers. Once the operation has been started the gases evolved in the reducing chamber are collected at the top of the said chamber and caused to. descend through the combustion chambers 11, where they burn, with the heated air, as above described, the waste gases being collected at the bottom of the chambers 11 for use elsewhere. The gases thus evolved in the reducing chambers and burned in the combustion chambers form the principal or sole (according to the metal contents of the ore) heating medium of the ore and carbon charge undergoing endothermic reaction in the" reducing chamber, except, as abovestated, on starting the furnace, when an external source of heat is employed.

According to the present invention therefore the order of operation of standard practice is entirely reversed. The ore is charged at the bottom of the reducing chamber and caused to traverse to the top of such chamber; the hottest zone is at the top and the lowest temperature is at the bottom, and the process is directed to produce the maximum amount of CO in the exit gases which have performed their function of reduction, and it is in this reversal that vast economies are effected in that much less carbon is consumed than in the blast furnace.

The CO gas formed by the reaction of carbon on the ore together with other gases ascends through a progressively hotter charge, and not through a progressively colder charge, as in existing ractice. The heat required for reaction 0 carbon on the ore is the potential heat of the gases formed by such reaction; these gases are burned in a chamber, the heat being conducted therefrom to the ore and carbon charge in such manner that the maximum heat is applied at the top of the charge.

It has been found that by adopting ordinary methods of heat recuperation from the exit gases the potential heat of such CO gas evacuated from the reducing chamber is sufficient to heat the ore-carbon charge together with supplying heat absorbed in the reaction to such a temperature requisite for the production of granular iron.

By this invention the coal containing the necessarycarbon for reducin the ore furnishes sufficient gas" to heat t e charge sufficiently for the required reaction, thus obviating the need of using extraneous sources of heat supply, such as is ordinarily provided by electricity or the combustion of fuel within or exteriorily of the chamber containing the ore charge.

The granular product at its maximum tern perature of 1,100 centigrade does not become viscid nor does it flux.

Burning the gases at the top of the combustion chamber and causing the hot products of combustion to descend inthe combustion chamber in contra-flow to the upward I movement of the ore-carbon charge bein heated permits of the maximum uni orm di ference in temperature bein maintained between the external heat of t e gases and the internal heat of the ore-carbon charge from top to bottom, that is to say the ore-carbon charge reaches a temperature of 1,000 at the top of the inner retort, whereas the gas burnt in the adjoining combustion chamber attains a temperature of approximately 1,600 C. Upon these burning gases' giving up their heat in course of descent the temperature at the bottom of the combustion chamber is thereby reduced to some 500 C. whereas the ore-carbon charge at this bottom extremity in the inner retort starts from cold. Therefore there is always an a proxim ately uniform difference from top to ottom of some 400-600" between the temperature of the burning gases and the temperature of the ore-carbon charge. This is the secret of rapid heat transmission and a factor which materially expedites the reduction process.

The apparatus described in connection with the present invention is claimed separately in my pending patent application S. No. 382,346.

What I claim and desire toisecure by Letters Patent is 1. Method of reducing iron ores consisting in introducing a charge of ore and carbon into the reducing chamber at the base thereof, raising the charge through progressively hotter zones inside the said chamber, collecing the gases evolved in the reducing chamber, at the top thereof, and burning the said gases in admixture with air in a separate combustion chamber disposed alongside the reducing chamber, the direction of movement of the burning gases being opposite to that of the movement of the ore charge.

' 2. Method of reducing iron ores consisting in introducing a charge of ore carbon and lime into the reducing chamber at the base thereof, raising the charge through progressively hotter zones inside the said chamber, collecting the gases evolved in the reducing chamber, at the top thereof, and burning the said gases in admixture with air in a separate combustion chamber disposed alongside the reducing chamber, the direction of movement of the burning gases being opposite to that of the movement of the ore charge, and discharging the reduced metal at the top of the reducing chamber.

3. Method of reducing iron ores consisting in introducin a charge of ore carbon and chalk into the re ucing chamber at the base thereof, raising the charge through progressively hotter zones inside the said chamber, collecting the gases evolved in the reducing chamber, at the top thereof, and burning the said gases in admixture with air in a separate combustion chamber disposed alongside the reducing chamber, the direction of movement of the burning gases being opposite to that of the movement of the ore charge.

In testimony whereof I afix my signature.

K-REDERMIK LIINDILEY DUN-HELD. 

